This invention relates to an internal combustion engine and more particularly to an improved induction system for an internal combustion engine.
For a number of years it has been recognized that the volumetric efficiency of an engine can be improved by using multiple intake valves for a given engine chamber. The use of such multiple valves permits a high effective cross sectional area for the induction system without abnormally high inertia loadings. That is, the use of two intake valves permits better volumetric efficiency and higher engine speeds than would be possible with a single induction system and single valve of corresponding cross-sectional area. With an engine embodying two intake valves, it is necessary to position the spark plug centrally of the combustion chamber. With arrangements of the type heretofore proposed, this spark plug location coupled with the direction of intake charge flow may not be satisfactory to provide good combustion at all engine speeds and loads.
More specifically, it is readily acknowledged that low speed performance of engines having a relatively large induction system is poor due to the sluggish air flow into the chamber at low speeds and the relatively low air flow into the chamber at the time of ignition. Although such devices as squish zones may be employed to improve turbulence, the use of large squish areas adversely affects the control over the emission on unwanted exhaust gas constituents. Furthermore, such an arrangement is not completely satisfactory in combination with a centrally positioned spark plug.
It is, therefore, a principal object of this invention to provide an inproved induction system for an internal combustion engine.
It is another object of this invention to provide an induction system for a dual intake valve equipped engine in which turbulence at low speeds is promoted.
It is a yet further object of the invention to provide an induction system for an internal combustion engine that promotes high volumetric efficiency and yet which provides for controlled flow in the combustion chamber at the time of ignition.
With the increased complexity of internal combustion engines, particularly those embodying the ancillary equipment required to provide good efficiency and exhaust emission control, the spacial requirements of the engine have become extremely critical. The positioning of such components as the throttle valves, particularly with engines embodying a multiple throttle valve in an induction tract is one problem that presents itself to an engine designer.
It is therefore, a further object of this invention to provide an improved, compact throttle valve arrangement for an internal combustion engine.